unison
by splendidlyimperfect
Summary: Ever since a traumatic incident in their youth, Gray has been able to borrow Natsu's power when he needs it. As he grows up, he begins to realize that it might mean something more. / Written for Gratsu Week 2k18 Day 1, Prompt: Magic


The first time it happens, they're nine years old. They're actually cooperating for once, which is both suspicious and a miracle. Ever since day one they've been at each other's throats, and while Master knows there's no real malice behind their blows, he does wish they would perhaps...tone it down a bit. For the sake of the guild building.

Today they're on a mission. Not a _real_ mission because they're too young to go hunting down yetis or saving theatre troupes quite yet, but Gramps has asked them to deliver a package to a nearby village and that sounds like a mission to them. Gray has drawn them a poster and everything, and the reward, scrawled in his mostly legible writing, says: _Natsu will say Gray is the greatest mage_. The only reason Natsu has agreed to this is because Gray has told him that it says _We both get free dinner_ , and Natsu can't read yet.

"Natsu, let's go!" Gray's got his arms crossed over his bare chest, scowl on his face as Natsu comes barreling down the road, enormous bag on his back. "How much food do you _have_ in there?"

"Well, I thought we might get lost," Natsu admits, already tearing into something and speaking around the crumbs. "So I brought enough for a week. Just in case."

"We're not going to get lost," Gray sighs, rolling his eyes as best he can. Logic dictates that he could have picked someone else to come with him on this adventure – Erza, for example – but if he's being honest, he like spending time with Natsu. He might be completely food obsessed and okay, there's the whole thing where his dad's a dragon, but in the end he's really strong and they work well together. Not that Gray will ever admit this out loud.

"Is that a map?" Natsu asks excitedly as Gray pulls a folded square sheet out of his pack. "Lemme see!" Gray hands it to him shyly as they walk away from the guild, toward the outskirts of town. He's hand-drawn the map, filled in intricate detail with each home, shop, river and town fixture. Natsu's eyes grow big as they scan over it and he nearly trips over a tree root. Gray reaches out an arm to steady him.

"Did you draw this?" Natsu looks up at Gray and there's something like awe in his eyes. Gray's noticed this sometimes – when they're not around anyone else, it's different. Less name-calling. More praise. Less fighting each other, and more fighting together.

"Yeah," he says softly, taking the map back from Natsu and folding it carefully, then sliding it back into his pack. He's so close to talking about his family – how dad taught him to read the stars, how mom showed him north from south, and how Ur helped him calculate distances by using the heights of trees. But it's only been a year and he misses them so much and he doesn't want to cry in front of Natsu, so he doesn't.

"Igneel and me didn't need a map," Natsu grinned, pointing upward. "We could just fly up and up and up and see _everything_." His eyes look sad for a second and Gray's hand is on his forearm again before he can think. He jerks it away quickly, but not before seeing a strange expression on Natsu's face.

They spend the rest of the afternoon in companionable conversation, and Gray finds himself glancing over at Natsu a lot. There's a bruise on his left jaw – that Gray gave him – in its last stages of healing, and his lip is still split from their last fight. The pink-haired boy talks with his hands and shows off his fire magic every chance he gets.

It's getting close to evening when something rustles in the bushes behind them. They're both immediately in defensive stances, magic summoned to their fingertips, when a man steps out ahead of them.

"What in the hell's a coupl'a kids doing out here?" he asks, almost conversationally, and Gray _knows_ they're in trouble. He's an unpleasant-looking man with long, greasy hair and a sly grin.

"We're not kids, we're on a quest!" Natsu says, glaring hard at the man. "We're gon-"

Gray quickly slaps a hand over Natsu's mouth before he can reveal any critical information about their mission and the man laughs, tipping his hat to the boys. Gray hears more crackling and realizes with a sinking heart that they're surrounded.

"Now, now, children," the man says sweetly, holding out his hand. "We know what you've got, just give it to us and we'll call it a draw."

Gray yelps as Natsu bites his hand, then snarls at the man, "We're Fairy Tail wizards! We won't give anything to you!"

The fight is surprisingly short because, while Gray and Natsu are children, they have magic that the bandits don't. Eventually it's just the three of them left and the man manages to catch Natsu in the stomach with a dagger while he has his back turned. Natsu's eyes widen in surprise as he stumbles into Gray's arms, then sinks to his knees.

"Now. I don't like having to hurt children, but you're giving me no choice." Gray's eyes are wide in fear and he can feel Natsu bleeding through their hands that are both pressed against the wound on his side. Fear is blistering through him and he holds a hand out toward the man, warning him against coming any closer.

"Leave us ALONE!" He shouts, closing his eyes and expecting a weak blast of cold. Instead, he feels _fire_ raging up and down his arm, brilliant blue flames intermingled with ice. The magic streams out of him, slamming into the man's chest and throwing him up into a tree. His head slumps forward and Gray feels the magic release, flooding back into him and concentrating itself, for just an instant, into a tiny flame in the middle of his palm.

He doesn't tell anyone. Instead he carries the unconscious Natsu back to the guild and is credited with saving his life, even though Natsu maintains later that he only faked being unconscious so he didn't have to walk. He doesn't even make Natsu say, "Gray is the best mage", because when Natsu stops bleeding and opens his eyes, all Gray can do is cry.

Master gives them both a stern lecture that is thoroughly undermined by the reward they receive from the city of Magnolia for stopping the bandits. They're heroes for a while, and Natsu has a cool new scar to show everyone. Gray just can't stop thinking about that tiny flame in the middle of his palm.

* * *

They go back to fighting. There's less harshness in their words – more companionship, less irritation – and Gray can _feel_ it now, a weird undercurrent when his magic touches Natsu's. It's heady and addictive and as the years go by, he picks more and more fights just to feel that sensation.

The next time it happens they're fourteen, and this quest is taken with Gramps' blessing. Erza's been threatening to beat them unconscious for weeks – something about their constant bickering – so they pack up their bags and head into the mountains. This time Gray doesn't have to make the reward poster because it's a real one, although he does bet Natsu that he'll collect more iceflowers and Natsu will have to say, "Gray is the best mage".

Gray brings a map and Natsu brings enough food for about three weeks, and it feels just like when they were kids. They spend the day collecting the blossoms – said to create the finest wine in the region – and they're on their way back to the town when a snowstorm comes in and they lose their way.

"I'm sure this is just wonderful for _you,"_ Natsu shouts, hand held in front of his face to block the snow whipping around him. He's flared up his magic around him to keep him warm, and Gray's nearly immune to the cold, so they're doing okay for now, but neither of them has any idea which way is north. The snow is blowing so hard they can barely see a foot in front of them and they're holding hands to keep from getting separated.

"Maybe we just need to – Natsu!" Gray shouts as the hand in his slips out and disappears. He drops to his knees, feeling around for Natsu but finding the edge of a large hole instead. "Natsu!" He shouts into the opening, tilting his head to hear a response over the howling wind. He's fairly certain he hears a groan and he sighs, feeling the edge of the hole and lowering himself in.

It's not a far drop into the cave and Gray pulls out a magelight, shaking it quickly to get it started. It illuminates a small, dry cavern, and a very unconscious Natsu who is bleeding from his head.

"Shit," Gray whispers, setting the light down on the ground and turning Natsu over. The only wound seems to be on his temple from where he hit the ground, and Gray ices it over as best he can, then drags Natsu into the corner of the cavern. Without his flames, Natsu's skin is icy cold and his lips are turning blue.

Gray closes his eyes, trying to figure out how to fix this. He's already covered Natsu in both winter jackets, and even _he's_ starting to feel cold without his coat. Natsu's hand in his is terrifyingly still, and Gray feels tears starting to form in his eyes. His magic is useless here. He can't save Natsu. He can't make a fire and-

He's warm, suddenly. Opening his eyes, he blinks in confusion as he realizes that both he and Natsu are surrounded by flames. They're not orange, though – they're blue, and they don't burn like fire would. It's like being surrounded by a warm blanket, and it quickly puts Gray to sleep.

When they're rescued the next day, Gray doesn't tell anyone. He's never seen this happen with other mages, and he worries it's something...forbidden.

* * *

It takes Gray a long, long time to figure out what's happening. He's nearly seventeen when it hits him – he's watching Natsu at the guild and contemplating throwing something at him just to piss him off when he realizes that he's not staring. He's admiring. Ogling, even. The passive appreciation of Natsu's body as being one that is generally attractive became an active appreciation of _holy fuck Natsu is ripped and I want to touch him when we're not fighting._

"Yo, ice block! Your face is stupid, fight me!" For the first time in his life Gray ignores those words, choosing instead to turn an unattractive color of red and run from the room as fast as possible.

The feelings are so overwhelming and confusing that he decides to leave for a bit – take a smaller job on his own so he has some time to sort through his brain. Because he can't possibly have feelings for that idiot, can he? He's old enough to know about these kinds of things (namely because Gildarts had attempted to have an in-depth conversation with him and he'd extricated himself from the situation and gone to Gramps instead). He's knows that infatuation isn't abnormal, and while he can't say he's ever had thoughts like this about girls, he's also never felt this way about _Natsu_.

Or has he? The pink-haired boy's face fills his mind as he makes his way through an unfamiliar town, trying to find the contact for his quest. It's in a library, one of the grandest in Fiore, and the second he's done tracking down the rare book the librarian needs for him, he asks for her help.

She's a sweet lady who tips her head at him kindly when he asks about 'magic melding'. He's reluctant to describe the experience and sensation – still afraid that he's wandered into something taboo. But she just nods and leads him to a section at the back of the building, pulls out a book, and hands it to him.

The title is in Ishvan, of which he remembers little, but he muddles his way through the first few pages. It's on the subject of 'Unison Raids', which he's never heard of before. _Unison Raids,_ it says, _only happen when two mages are extremely compatible, either in terms of magic or personality._ He frowns. What they have isn't a Unison Raid. Natsu doesn't even know about it. Plus, fire and ice aren't exactly compatible.

"Perhaps that's what your magics want," the woman says kindly, seeing the pinkish color raise in Gray's cheeks. "Or what you want."

The librarian lets Gray keep the book. She gives it to him with his guild reward and he brings it home, leaving it on his bedside table and ignoring it (and his feelings) for several more years.

* * *

"Erza, get Lucy somewhere safe!" Natsu dodges a pincer and strikes upwards at the beast's stomach, causing it to howl and rear up on several of its legs. Gray takes the opportunity to throw an ice lance at it, piercing the sensitive skin of its underbelly.

The job, supposed to be a simple escort to a new settlement, is going poorly. Apparently, the new settlement is already populated – by giant, spider-like creatures with segmented legs and a poisonous bite. Erza is carrying Lucy away, and Gray can see a purplish-black mark from where the beast bit her.

"We have to flip it over!" he shouts down to Natsu, who nods and blasts the creature again from below. It staggers on six of its eight legs but doesn't topple completely. Gray can hear Natsu swear as one of the razor-sharp limbs slices across his arm. He hops backward, scrambling up towards where Gray is standing.

"That thing...is disgusting," he pants, hand clasped over the bleeding cut on his arm. Gray reaches over and touches his fingertip to the wound, letting a thin layer of ice cover it. It melts almost instantaneously – Natsu's skin is too hot – but it usually seems to help. "Thanks, ice cube."

"Mmm," Gray replies, keeping his eyes on the horrifying beast and not on Natsu's sweaty torso. "If we can flip it over we can take out it's underside?" His eyes dart from leg to leg to leg. "I could try to freeze the legs together? That might make it easier to flip?"

"Nice!" Natsu says, nudging him with his shoulder. "Let's get rid of this thing and go home."

They both hop down from the hill, skidding through the dirt and landing on either side of the beast. Gray immediately ices two legs together, but as he moves to add a third, the spider spins around towards him, knocking him aside.

"Hey! Over here!" Natsu shoots a few jets of fire at the beast, trying to draw its attention while Gray blasts it with ice, but it's quick, snapping at one of them and then the other. It skitters back and forth while they shoot magic at it, never truly penetrating its thick hide.

"Natsu, go now!" Gray draws the beast over to him and gestures for Natsu to slip underneath where it's vulnerable. The spider is smart, though, and it darts downward, snapping Gray up in its mandibles and tightening them with a sickeningly wet sound. Gray cries out in pain as twin wounds open up in both of his sides, blistering hot with the accompanying poison.

"GRAY!" The ground rushes up to him and he feels his breath leave him in a _whoosh_ as he hits it, back of his head bouncing once or twice before his vision settles. He makes an inarticulate sound of pain and then Natsu is there, grabbing his hand and tapping his cheek. "Shit, Gray, look at me. You're gonna be okay."

"N'su," he grinds out, gesturing to the beast which is rearing above them. Gray knows he can do it. He can take Natsu's magic and make himself strong enough to save them both, but that means telling Natsu. Means admitting his feelings. He's really starting to wish he'd done it sooner.

"Gray, I-"

"Let me-"

They both start talking at the same time and Gray frowns, seeing an unusually vulnerable expression on Natsu's face. His eyes are wet and his cheeks are pink and his hair is blown back out of his face, and Gray just wants nothing more than to kiss him before he dies from whatever horrible poison is currently destroying his body.

"I can use your magic," Natsu says, quietly, and Gray frowns.

Oh. So if he can...then...

"Me too," Gray replies, and Natsu's eyes widen. He grabs one of Gray's bloody hands, using his other to staunch one of his wounds, and stares at their entwined fingers intently. Then he gives Gray a half-smile, turns to the beast, and unleashes their joined magic.

It's magnificent. The sensation is nothing like the first few times – Gray can feel tendrils of flame and ice piercing every part of his body, and his skin is tingling with electricity. Blue flames burst from their fingertips, spiraling up and hitting the monster in the eyes. It screams, tossing its head back and forth and staggering on now-unsteady legs. Another burst of magic shoots icy daggers surrounded with flame, slashing at the legs and the feet and then driving all simultaneously into the soft, vulnerable underbelly.

The beast shudders for a moment, then twitches and slowly begins to fall. Gray feels the magic leave his body suddenly, as if in a huge rush, and he's left with only pain and darkness.

* * *

"Why didn't you say something?"

Gray winces, blinking slowly awake to the familiar sight of the infirmary roof. He's got the patterns on this ceiling memorized.

"Why..." he tilts his head and sees Natsu, sitting in a chair next to the bed, looking...terrible. His hair's a mess and his eyes are dark and Gray is fairly certain he hasn't changed in a while. A bandage is wrapped around his arm from where the beast got him. "Did we win?" He asks weakly.

"We did a Unison Raid," Natsu replies, smile ghosting over his lips. "So yeah, we won." Gray dropped Natsu's gaze, fiddling with a thread on the infirmary bed. "Why didn't you tell me?"

"I didn't..." Gray sighs, pushing himself until he's sitting. Natsu hands him a glass of water and he takes it gratefully. "I didn't think you felt the same."

"When did you know?" Natsu's voice is so quiet, with no judgement, just shy curiosity.

"First time was when we were kids. I saved your ass from that bandit." Gray smiles at the memory.

"Gray, that was...almost ten years ago!" Natsu looks incredulous and Gray's not sure if that's a good thing or a bad thing. "Shit. Didn't happen for me until...a few years ago, I guess. We were on some job and...you got hurt."

"I'm sensing a theme here," Gray says wryly, sitting up more and wincing. "So, what d-"

Natsu cuts him off by leaning over and kissing him. Gray's surprise is quickly overridden by instinct and he brings a hand to Natsu's hair, running his fingers through it as their lips press together. It's a short, tentative kiss, and when Natsu leans back into his chair his cheeks are red and his eyes are downcast.

"S-sorry if...I j-jus-"

"I liked it." Gray reaches out for Natsu's hand and twines their fingers together, squeezing. "The kiss _and_ the Unison Raid." Natsu exhales in relief and gives Gray a shy smile.

"So...wanna do it again?"

"Definitely," Gray says, grinning. "But I call dibs out on getting poisoned by a giant spider next time." Natsu snorts, leaning in against for another soft kiss.

"I think I can live with that."


End file.
